The only solution I have seen that might be effective for you is to look at our Vapor X model. We actually allow you to turn off two of the three fans at low usage loads to reduce noise even further. I can tell you that in my current setup even with three fans running I cannot heard the card at idle or under load. With the two fans hut down it is even quieter however.
While interesting, its a little out of reach considering I already have a card
I will keep The Vapor X range in mind for sure though if such features continue to exist when I am buying my next card.